Systems and methods for rfid security

ABSTRACT

An RFID system includes an RFID tag, an RFID reader, and a server. The RFID tag communicates to the server via encrypted information. The information may be encrypted with synchronized encryption keys. In this manner, the reader need not decrypt the information from the RFID tag. The effectiveness of malicious readers is thereby reduced, resulting in improved RFID tag security.

CROSS REFERENCE TO RELATED APPLICATIONS

This invention is a continuation of and claims priority from U.S. patentapplication Ser. No. 11/386,540, filed Mar. 21, 2006, naming KambizShoarinejad and Maryam Soltan as inventors, the contents of which ishereby incorporated herein by reference in its entirety.

BACKGROUND

The present invention relates to radio frequency identification (RFID),and in particular, to systems and methods for RFID security.

RFID systems are useful in a wide variety of applications. RFID systemsare radio communication systems that include small low cost electronicdevices that store information including identification (ID)information, for example. These devices are referred to as RFID tags.The RFID tags may be designed using backscattering circuit techniques,for example, so that another device can retrieve the ID wirelessly. Theretrieving device is typically referred to as a “reader”, and sometimesas an “interrogator”. The tags are typically very small, and may beplaced on a variety of items including equipment, products, or evenpeople, for example, and identification of such items may be madethrough a reader. Accordingly, RFID systems may be used to trackinventory in a warehouse, the number of products on store shelves, orthe location of equipment in a company, to name just a few exampleapplications.

RFID systems may include large numbers of tags and readers spread outacross potentially wide areas. The large number of tags and readers mayresult in a correspondingly large volume of information that may need tobe processed. Such information may include large volumes of tag IDs. Inorder to process such information, powerful readers are typically usedthat include complex software capable of interfacing with backendsystems that store and ultimately use the data.

The cost of RFID tags is decreasing in correspondence with advances insemiconductor processing and electronic circuitry technology. As such,RFID tags are being associated with a wide variety of items inincreasing numbers.

As RFID tags are being incorporated on an increasing number of items,privacy concerns arise. For example, RFID tags may be attached to retailproducts in a store. Competitors of the store may surreptitiously readthe RFID tags to obtain business intelligence regarding sales, turnover,etc. As another example, RFID tags may be attached to drivers' licenses.Entities may surreptitiously track people using such tags. RFID tags maybe incorporated with financial items such as currency, gaming tokens,bank cards, credit cards, gift cards, etc. Entities may surreptitiouslyread the information stored on the card and attempt to use thatinformation to perform unauthorized transactions.

These and other concerns provide a desire to improve the security ofRFID tags. However, adding security features to RFID tags increasestheir cost. A conflict arises between security of RFID tag informationand ubiquity of RFID tag deployment. Thus, there is a need for securityfeatures that may be implemented with low cost in an RFID system.

SUMMARY

In order to solve the above-noted problems and others, the presentinvention is directed toward systems and methods of securelytransferring information, authentication, or access control in an RFIDsystem.

According to one embodiment, a method transmits information between aRFID tag and a server. The method includes encrypting, by the RFID tagaccording to a predetermined scheme, identification data identifying theRFID tag, to result in encrypted RFID information. The method furtherincludes reading, by a RFID reader, the encrypted RFID information fromthe RFID tag. The method further includes receiving, by the RFID reader,authentication data. The authentication data authenticates the RFID tagto the server. The method further includes transmitting, from the RFIDreader to the server, a transmission that includes the encrypted RFIDinformation and the authentication data. The method further includesdecrypting, by the server according to the predetermined scheme, theencrypted RFID information to generate the identification data. Themethod further includes authenticating, by the server, the transmissionusing the authentication data and the identification data. The methodfurther includes authorizing, by the server, the transmission using theidentification data.

According to a further embodiment, the RFID tag is involved in atransaction involving the user of the RFID tag, the RFID reader, and theserver listed above.

According to another embodiment, an RFID system includes the RFID tag,the RFID reader and the server listed above, and implements the methoddescribed above.

According to another embodiment, the RFID tag and the server listedabove generate encryption keys for encrypting and decryptinginformation.

According to another embodiment, an RFID tag is part of an RFID systemthat also includes an RFID reader and a server. The RFID tag includes atransceiver and a processor. The transceiver communicates with the RFIDreader. The processor controls the operation of the RFID tag.

In another embodiment, the present invention includes a method oftransmitting information between a radio frequency identification (RFID)tag and a server, the method comprising the steps of encrypting, by theRFID tag according to a predetermined scheme, identification dataidentifying the RFID tag, to result in encrypted RFID information,reading, by a RFID reader, the encrypted RFID information from the RFIDtag, transmitting, from the RFID reader to the server, a transmission,wherein the transmission includes the encrypted RFID information, anddecrypting, by the server according to the predetermined scheme, theencrypted RFID information to produce the identification data.

In one embodiment, the present invention further comprises authorizing,by the server, the transmission using the identification data.

In one embodiment, the present invention further comprises receiving, bythe RFID reader, authentication data, wherein the authentication dataauthenticates the RFID tag to the server, and wherein the transmission,from the RFID reader to the server, includes the authentication data,authenticating the transmission using the authentication data and theidentification data by the server.

In one embodiment, the present invention comprises receiving, by theRFID reader, authentication data and transaction information, whereinthe authentication data authenticates the RFID tag to the server, andwherein the transaction information relates to a transaction involvingthe RFID tag and the RFID reader, and the step of transmitting comprisestransmitting, from the RFID reader to the server, the transmission,wherein the transmission includes the encrypted RFID information, thetransaction information, and the authentication data.

In one embodiment, the present invention further comprisesauthenticating, by the server, the transaction using the authenticationdata and the identification data, and authorizing, by the server, thetransaction using the identification data and the transactioninformation.

In one embodiment, the authentication data comprises a password,biometric information, or a pseudo-random number.

In one embodiment, the RFID tag displays an authentication code that auser of the RFID tag provides to the reader as the authentication data.

In one embodiment, the method further comprises activating the RFID tag,prior to the step of reading.

In one embodiment, the method further comprises activating the RFID tag,prior to the step of reading, with one of a switch, biometricinformation, or a password.

In one embodiment, the method further comprises generating, by the RFIDtag prior to the step of encrypting, a pseudorandom number, wherein thestep of encrypting is performed using the pseudorandom number.

In one embodiment, the method further comprises generating, by the RFIDtag prior to the step of encrypting, a first pseudorandom number,wherein the step of encrypting is performed using the first pseudorandomnumber; and generating, by the server prior to the step of decrypting, asecond pseudorandom number, wherein the second pseudorandom numbercorresponds to the first pseudorandom number, and wherein the step ofdecrypting is performed using the second pseudorandom number.

In one embodiment, the method further comprises performing, by theserver, synchronization contingency processing when the step ofdecrypting results in a failure.

In one embodiment, the method further comprises communicating, by thereader, timing information to the RFID tag, and updating, by the RFIDtag, an encryption key using the timing information, wherein theencryption key is used in the step of encrypting.

In one embodiment, the method further comprises communicating, by theserver, timing information to the RFID tag, and updating, by the RFIDtag, an encryption key using the timing information, wherein theencryption key is used in the step of encrypting.

In one embodiment, the RFID tag stores a first plurality of encryptionkeys, wherein the server stores a second plurality of encryption keys,wherein the first plurality of encryption keys corresponds to the secondplurality of encryption keys, further comprises communicating, by theserver via the reader, a pointer to the RFID tag, wherein the pointerpoints to a selected one of the first plurality of encryption keys,wherein the RFID tag uses the selected one of the first plurality ofencryption keys when encrypting, and wherein the server uses acorresponding selected one of the second plurality of encryption keyswhen decrypting.

In one embodiment, the RFID tag stores a first plurality of encryptionkeys, wherein the server stores a second plurality of encryption keys,wherein the first plurality of encryption keys corresponds to the secondplurality of encryption keys, further comprises communicating, by thereader, a pointer to the RFID tag, wherein the pointer points to aselected one of the first plurality of encryption keys, and wherein theRFID tag uses the selected one of the first plurality of encryption keyswhen encrypting; and communicating, by the reader, the pointer to theserver, wherein the pointer points to a corresponding selected one ofthe second plurality of encryption keys, and wherein the server uses thecorresponding selected one of the second plurality of encryption keyswhen decrypting.

In one embodiment, the server generates an encryption key and transmitsthe encryption key to the RFID tag, wherein the RFID tag uses theencryption key when encrypting, and wherein the server uses theencryption key when decrypting.

In one embodiment, the server generates an encryption key and transmitsthe encryption key to the RFID tag, wherein the RFID tag updates theencryption key according to a defined process to result in an updatedencryption key, wherein the RFID tag uses the updated encryption keywhen encrypting, wherein the server updates the encryption key accordingto the defined process to result in the updated encryption key, andwherein the server uses the updated encryption key when decrypting.

In one embodiment, the step of reading is performed by backscattering.

In another embodiment, the current invention includes a radio frequencyidentification (RFID) system, the RFID system comprising an RFID tag, anRFID reader that communicates with the RFID tag, and a server thatcommunicates with the RFID reader, wherein the RFID tag encrypts,according to a predetermined scheme, identification data identifying theRFID tag, to result in encrypted RFID information, wherein the RFIDreader reads the encrypted RFID information from the RFID tag, whereinthe RFID reader transmits a transmission to the server, wherein thetransmission includes the encrypted RFID information, and wherein theserver decrypts, according to the predetermined scheme, the encryptedRFID information to produce the identification data.

In one embodiment, the server authorizes the transmission using theidentification data.

In one embodiment, the RFID reader receives authentication data, whereinthe transmission, from the RFID reader to the server, includes theauthentication data, and wherein the authentication data authenticatesthe RFID tag to the server.

In one embodiment, the server authenticates the transmission using theauthentication data and the identification data.

In one embodiment, the RFID reader receives the authentication data andtransaction information, wherein the transaction information relates toa transaction involving the RFID tag and the RFID reader, thetransmission includes the encrypted RFID information, the transactioninformation, and the authentication data, the server authenticates thetransaction using the authentication data and the identification data,and the server authorizes the transaction using the identification dataand the transaction information.

In one embodiment, the RFID tag comprises a transceiver thatcommunicates with the RFID reader, and a processor, coupled to thetransceiver, that encrypts, according to the predetermined scheme, theidentification data.

In one embodiment, the RFID tag comprises a transceiver thatcommunicates with the RFID reader, a memory that stores a plurality ofencryption keys, and a processor, coupled to the transceiver and to thememory, that encrypts, according to the predetermined scheme, theidentification data using a selected one of the plurality of encryptionkeys.

In one embodiment, the RFID tag comprises a switch that activates theRFID tag, a transceiver that communicates with the RFID reader when theRFID tag is active, and a processor, coupled to the switch and to thetransceiver, that encrypts, according to the predetermined scheme, theidentification data.

In one embodiment, the RFID tag comprises a switch that activates theRFID tag, wherein the switch includes one of a physical toggle, abiometric sensor, or a password processing system, a transceiver thatcommunicates with the RFID reader when the RFID tag is active, and aprocessor, coupled to the switch and to the transceiver, that encrypts,according to the predetermined scheme, the identification data.

In one embodiment, the RFID tag comprises a transceiver thatcommunicates with the RFID reader, a processor, coupled to thetransceiver, that encrypts, according to the predetermined scheme, theidentification data, and a display, coupled to the processor, thatdisplays an authentication code that a user of the RFID tag provides tothe RFID reader as the authentication data.

In another embodiment, the present invention includes a method oftransmitting information between a radio frequency identification (RFID)tag and a server, the method comprising the steps of transmittingidentification data from the RFID tag to an RFID reader, receiving, bythe RFID reader, authentication data, wherein the authentication dataauthenticates the RFID tag to the server, transmitting, from the RFIDreader to the server, a transmission, wherein the transmission includesthe identification data and the authentication data, and authenticating,by the server, the transmission using the authentication data and theidentification data.

In one embodiment, the authentication data comprises a password.

In one embodiment, the authentication data comprises biometricinformation.

In one embodiment, the authentication data comprises a pseudo-randomnumber.

In one embodiment, the pseudo-random number is generated by the RFID tagand displayed to a user, and wherein the server includes a synchronizedpseudo-random number.

In another embodiment, the present invention includes a method oftransmitting information between a radio frequency identification (RFID)tag and a RFID reader, the method comprising the steps of receiving, bythe RFID tag from the RFID reader, first information, displaying atleast a portion of the first information to a user, receiving averification from the user to verify the first information, andtransmitting identification data from the RFID tag to the RFID reader ifthe first information has been verified.

In one embodiment, the step of receiving a verification comprisesactivating a switch on the RFID tag to verify the first information.

In one embodiment, the first information comprises information about atransaction.

In one embodiment, the first information comprises a number or a code.

In one embodiment, the first information comprises an image.

In another embodiment, the present invention includes a radio frequencyidentification (RFID) tag for use in an RFID system including an RFIDreader and a server, the RFID tag comprising a transceiver thatcommunicates with the RFID reader, and a processor, coupled to thetransceiver, that generates a pseudorandom number according to apredetermined scheme, and that encrypts identification data identifyingthe RFID tag using the pseudorandom number.

In one embodiment, the RFID tag further comprises a switch foractivating the RFID tag.

In one embodiment, the RFID tag further comprises a switch, where theRFID tag receives information from a reader, and a user verifies theinformation from the reader and activates the tag using the switch, andthe RFID tag transmits information to the reader only if the userverifies the information from the reader.

In one embodiment, the RFID tag further comprises a display, and theRFID tag receives information from a reader and displays the informationto a user.

In one embodiment, the RFID tag further comprises a display, coupled tothe processor, that displays the pseudorandom number.

In another embodiment, the present invention includes a radio frequencyidentification (RFID) tag for use in an RFID system including an RFIDreader and a server, the RFID tag comprising a transceiver thatcommunicates with the RFID reader, a processor, coupled to thetransceiver, that encrypts, according a predetermined scheme,identification data that identifies the RFID tag, and that generates anauthentication code, and a display, coupled to the processor, thatdisplays the authentication code.

In one embodiment, the RFID tag further comprises a switch foractivating the RFID tag.

In one embodiment, the RFID tag further comprises a switch, where theRFID tag receives information from a reader, and a user verifies theinformation from the reader and activates the tag using the switch, andthe RFID tag transmits information to the reader only if the userverifies the information from the reader.

In one embodiment, the RFID tag receives information from a reader anddisplays the information to a user.

In one embodiment, the RFID tag displays the information from the readerto the user before the RFID tag sends an encrypted identification datato the reader.

In another embodiment, the present invention includes a radio frequencyidentification (RFID) tag for use in an RFID system including an RFIDreader, the RFID tag comprising a switch for activating the RFID tag, atransceiver that communicates with the RFID reader, and a processor,coupled to the transceiver, that processes information received from theRFID reader.

In one embodiment, the present invention further comprises a display,coupled to the processor, that displays information received from theRFID reader.

In one embodiment, the RFID tag receives first information from the RFIDreader and displays at least a portion of the first information to auser, and wherein identification data is transmitted from the RFID tagto the RFID reader if the first information has been verified using theswitch.

In one embodiment, the RFID tag receives first information from the RFIDreader if the switch is activated and the transceiver is disabled if theswitch is deactivated.

The following detailed description and accompanying drawings provide abetter understanding of the nature and advantages of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an RFID system according to an embodimentof the present invention.

FIG. 2 is a block diagram of a method of operation of an RFID systemaccording to an embodiment of the present invention.

FIG. 3 is a block diagram of a method of key generation according to anembodiment of the present invention.

FIG. 4 is a block diagram of a method of key generation according toanother embodiment of the present invention.

FIG. 5 is a block diagram of a method of key generation according toanother embodiment of the present invention.

FIG. 6 is a block diagram of a method of key generation according toanother embodiment of the present invention.

FIG. 7 is a block diagram of an RFID tag according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

Described herein are techniques for security in an RFID system. In thefollowing description, for purposes of explanation, numerous examplesand specific details are set forth in order to provide a thoroughunderstanding of the present invention. It will be evident, however, toone skilled in the art that the present invention as defined by theclaims may include some or all of the features in these examples aloneor in combination with other features described below, and may furtherinclude obvious modifications and equivalents of the features andconcepts described herein.

Described herein are various methods and processes. Although the stepsmay be presented in a particular order, such order is shown forconciseness of description. Such order is not required except when alater step absolutely requires that a previous step be completedbeforehand. As such, the steps may be performed in another order, inparallel, etc.

FIG. 1 is a block diagram of an RFID system 100 according to anembodiment of the present invention. The RFID system 100 includes anRFID tag 102, a reader 104, and a server 106. The RFID tag 102 may beone of numerous RFID tags, the reader 104 may be one of numerousreaders, and the server 106 may be one of numerous servers; one of eachis shown for conciseness in the figure. The RFID tag 102 communicateswith the reader 104 over a wireless link 108. Examples ofimplementations of the link 108 include a Bluetooth link, anultrawideband (UWB) link, a backscattering link, or an optical link. Thereader 104 communicates with the server 106 over a link 110. The link110 may be a direct link (such as a dedicated wire link or a dedicatedwireless link) or an indirect link (such as via a telecommunicationsnetwork or the internet).

The following security concerns arise given the RFID system 100. Oneconcern is the security of the link 110 from eavesdropping. Anotherconcern is the security of the link 108 from eavesdropping or otherwiseunrestricted reading of the RFID tag 102. Another concern isauthentication of the reader 104 to the server 106. Another concern isunauthorized access to the RFID tag 102 by a reader other than thereader 104. Another concern is unauthorized access to the end-to-endtransaction between the RFID tag 102 and the server 106. The presentinvention is directed toward addressing these and other securityconcerns.

FIG. 2 is a block diagram of a method 120 that describes the operationof the RFID system 100 (see FIG. 1) according to an embodiment of thepresent invention. In step 122, the RFID tag 102 encrypts identificationdata that identifies the RFID tag 102. The encrypted identification datamay be referred to as encrypted RFID information. The encrypted RFIDinformation may also include other information related to the RFID tag102. The RFID tag 102 encrypts the data according to a predeterminedscheme. Less than all of the data to be read from the tag may beencrypted if so desired.

In step 124, the reader 104 reads the encrypted RFID information fromthe RFID tag 102. Such reading may occur via backscattering, Bluetoothcommunications, UWB communications, optical reading, etc.

In step 126, the reader 104 receives authentication data that the serveruses (see step 132 below) to authenticate the reader 104. Theauthentication data may be in the form of a code, a password, a personalidentification number (PIN), or biometric information such as afingerprint, etc. that the user of the RFID tag 102 may provide to thereader 104. The authentication data may also be or include apseudorandom component. The pseudorandom component may be generated anddisplayed by the RFID tag 102 itself or by another device.

The authentication data assures that the reader 104 has been authorizedby the user for a particular reading. For example, when the tag 102 isin an area with multiple readers, it may be read by more than onereader. The authentication data associates the RFID tag 102 with thereader 104, and the other readers will lack the authentication data.Similarly, if a malicious reader collects data by surreptitiouslyreading tags, the malicious reader will lack the authentication data,and will be unable to provide it to the server for authentication (seestep 132 below). Thus, even though the RFID tag 102 may be read by amalicious reader, the malicious reader can do nothing with theinformation.

In step 128, the reader 104 transmits the encrypted RFID information andthe authentication data to the server 106. The transmission from thereader 104 to the server 106 may itself be encrypted. Such encryptionmay be performed using an algorithm unrelated to the RFID processingotherwise discussed in this patent disclosure. Such encryption may alsobe performed using information related to the RFID processing discussedin this patent disclosure; for example, the transmission from the reader104 to the server 106 may be encrypted using the authentication data.

In step 130, the server 106 decrypts the encrypted RFID informationaccording to the predetermined scheme to produce in the identificationdata. The server 106 may use the identification data to associate theRFID tag 102 with other stored data. For example, a bank server mayassociate the identification data from the RFID tag 102 with an accountnumber associated with the user's bank account.

In step 132, the server 106 authenticates the transmission from thereader 104 using the authentication data and the identification data.The server 106 has a database that associates the identification datawith target authentication data. If the authentication data includes apseudorandom component, the server 106 also generates a targetpseudorandom component according to the same scheme used by the RFID tag102. The server 106 then compares the authentication data from thereader 104 with the target authentication data to authenticate thetransmission. For example, if the authentication data is a PIN, theserver 106 compares the PIN to a target PIN associated with theidentification data. If the PIN from the reader matches the target PIN,the transmission from the reader is authenticated. The server 106 maytransmit an acknowledgement to the reader 104 to indicate whether thetransmission has been authenticated. After the transmission has beenauthenticated, the method 120 proceeds to step 134.

In step 134, the server 106 authorizes the transmission from the reader104 using the identification data. The server 106 may transmit anacknowledgement to the reader 104 to indicate whether the transmissionhas been authorized.

Alternatively, the authentication step may be performed before thedecryption step in cases where the server 106 receives information fromthe reader 104 sufficient to perform the authentication.

The method 120 may be used to authorize a transaction involving the RFIDtag 102 and the reader 104. For example, the RFID tag 102 may beincorporated in a bank card, and the reader 104 may be a point of saleterminal in a store. In step 126 additionally, the reader 104 mayreceive transaction information, for example, a dollar amountcorresponding to a purchase the user desires to make. In step 128additionally, the reader 104 transmits the transaction information tothe server 106. In step 132 additionally, the server 106 authenticatesthe transaction. In step 134 additionally, the server 106 authorizes thetransaction, for example, by debiting the user's bank account balance bythe dollar amount of the transaction and by crediting the store. Theserver 106 may acknowledge, for example, the user's new balance to thereader 104.

According to other embodiments, the encryption key may be modified asdesired. According to a first option, the encryption key may be used fora defined period of time (which may be referred to as a “validityperiod”). According to a second option, a different encryption key maybe used each time the tag is read. According to a third option, adifferent encryption key may be used depending upon the type of readrequest that the tag receives.

FIGS. 3-6 concern various methods of selecting or generating anencryption key (also referred to as a “key”). The key may be generatedas a pseudorandom number. The key may be used for encryption (step 122of FIG. 2) and decryption (step 130 of FIG. 2).

FIG. 3 is a block diagram of a method of key generation according to anembodiment of the present invention. This method is suitable for usewhen the RFID tag 102 has a continuous source of power.

In step 150, the server 106 generates a pseudorandom number (“PRN”)according to a predetermined scheme. The predetermined scheme mayinvolve bit shifting, transforming, or logically operating upon apreviously-generated pseudorandom number. The scheme may involvecomputing the pseudorandom number at a defined rate.

In step 152, the RFID tag 102 generates a pseudorandom number accordingto the predetermined scheme. Since the RFID tag 102 and the server 106generate their pseudorandom numbers according to the same scheme, thepseudorandom numbers will match.

In step 154, the RFID tag 102 encrypts the identification data using thepseudorandom number. For example, the RFID tag 102 may perform anexclusive OR operation on the identification data and the pseudorandomnumber as the encryption operation. The pseudorandom number may be usedfor a defined validity period, for example one minute, before the nextpseudorandom number resulting from the scheme is used for encryption.

In step 156, the server 106 decrypts the encrypted RFID informationusing the pseudorandom number. For example, the server 106 may performan exclusive OR operation on the encrypted RFID information and thepseudorandom number as the decryption operation. If the decryption failsor otherwise results in meaningless data, the method proceeds to step158.

In step 158, the server 106 performs synchronization contingencyprocessing. If the decryption of step 156 fails, it may be because theserver has updated its pseudorandom number in the time the reader 104was reading the RFID tag 102, or because of delays in transmission fromthe reader 104 to the server 106, or because the RFID tag 102 and theserver 106 are out of synchronization. For example, if the RFID tag 102is read near the end of the validity period, the server 106 may notreceive the encrypted RFID information until the next validity periodhas been entered. To resolve these issues, the server 106 uses one ormore of the previous (or next) pseudorandom numbers to perform thedecryption of step 156. If the decryption still fails, this indicatesthat the transmission may be unauthorized or that the circuitry of theRFID tag 102 may be defective.

As can be seen from the above description, the method of FIG. 3 issuitable for use when the PRN in RFID tag 102 is reasonably synchronouswith respect to the server 106. The process otherwise occurs asdescribed above regarding FIG. 2.

FIG. 4 is a block diagram of a method of key generation according toanother embodiment of the present invention. This method is suitable foruse when the RFID tag 102 does not have a continuous source of power.

In step 170, the reader 104 communicates timing information to the RFIDtag 102. This communication may occur when the reader 104 is reading theRFID tag 102.

In step 172, the RFID tag 102 compares the timing information receivedin step 170 with stored timing information from the last time the RFIDtag 102 was active. This comparison may result in a timing interval. Forexample, if the stored timing information is 12:00:00 and the timinginformation communicated in step 170 is 12:50:00, the timing interval is50:00.

In step 174, the RFID tag 102 computes the pseudorandom number using thepredetermined scheme (see step 152 in FIG. 3), further according to thetiming interval. Namely, the use of the timing interval allows the RFIDtag 102 to compute the pseudorandom number as if it had beencontinuously computing the pseudorandom number over the period that theRFID tag 102 has been inactive.

For example, assume that the RFID tag 102 takes 0.001 seconds togenerate the next pseudorandom number given the present pseudorandomnumber, for a given validity period. Assume that the validity period is100 seconds, and that the timing interval is 100,000 seconds. Thus, 1000validity periods have passed since the RFID tag 102 was last active. TheRFID tag 102 then takes 1 second to execute the 1000 generationoperations necessary to generate the current pseudorandom number. Inanother embodiment, timing information may be transmitted from theserver to the tag via the reader.

The process otherwise occurs as described above regarding FIG. 2.

FIG. 5 is a block diagram of a method of key generation according toanother embodiment of the present invention. This method is suitable foruse when the RFID tag 102 does not have a continuous source of power.

To set up the method of FIG. 5, assume that the server 106 stores a setof encryption keys and that the RFID tag 102 stores a copy of the set ofencryption keys. The encryption keys may be referenced by a pointer.Thus, if the server 106 selects one of the encryption keys to use, itmay communicate the pointer to the RFID tag 102, which may then selectthe corresponding encryption key using the pointer.

In step 190, the server 106 sends to the reader 104 a pointer to one ofa set of encryption keys stored by the server 106. The encryption keysmay be pseudorandom numbers. In step 192, the reader 104 transmits thepointer to the RFID tag 102. This transmission may occur when the reader104 is attempting to read the RFID tag 102. In step 194, the RFID tag102 uses the pointer to identify a corresponding encryption key from itsown stored set of encryption keys. This set corresponds to the setstored by the server 106, so both encryption keys match.

The process otherwise occurs as described above regarding FIG. 2.

Alternatively, the reader 104 may select the pointer. In such case, thereader 104 informs the server 106 of the pointer selected, for example,as part of the transmission step 128 (see FIG. 2).

FIG. 6 is a block diagram of a method of key generation according toanother embodiment of the present invention. This method is suitable foruse when the RFID tag 102 does not have a continuous source of power.

In step 210, the reader 104 reads preliminary information from the RFIDtag 102. The preliminary information may be a partial tag ID. In step212, the reader 104 transmits the preliminary information to the server106. In step 214, the server 106 uses the preliminary information togenerate or select an encryption key, which may be a pseudorandomnumber. In step 216, the server 106 sends the encryption key to thereader 104. In step 218, the reader 104 sends the encryption key to theRFID tag 102.

The process otherwise occurs as described above regarding FIG. 2.

Alternatively, the server 106 and the RFID tag 102 may use thecommunicated encryption key as a starting point to generate, accordingto a common scheme, a pseudorandom number for use in encrypting anddecrypting. As discussed above, since each pseudorandom number isgenerated according to the same scheme, the pseudorandom numbers willmatch.

As a further alternative, the server 106 may select a pointer in step214. In such case, the method proceeds in a manner similar to thatdescribed above in FIG. 5.

FIG. 7 is an example block diagram showing components that may beincluded on an RFID tag 102 according to an embodiment of the presentinvention. The RFID tag 102 may include a transceiver 230, a processor232, a memory 234, a switch 236, a display 238, and a power supply 240.These components may be composed of one or more circuit elements. It isto be understood that some tags may not include all of these components(e.g., power supply 240).

The transceiver 230 wirelessly links the RFID tag 102 with the reader104. If the RFID tag 102 is an active tag, the transceiver 230 maytransmit radio signals. If the RFID tag 102 is a passive tag, thetransceiver 230 operates according to backscattering.

The processor 232 controls the operation of the RFID tag 232. Forembodiments that involve pseudorandom numbers, the processor 232generates the pseudorandom numbers. The processor 232 may receive timinginformation from an oscillator (not shown).

The memory 234 stores information used by the RFID tag 102. Suchinformation may include the tag ID or other identification information,a set of pointers and encryption keys (see FIG. 5 and relateddescription), and other information.

The switch 236 controls activation of the RFID tag 102. (If activationcontrol of the RFID tag 102 is undesired, the switch 236 may beomitted.) The switch 236 may be implemented as a button, as a toggleswitch, as an input processing system (for example, for entering a PIN,code or password), or as a biometric processing system (for example, forcomparing an input fingerprint with stored data of the user'sfingerprint), or another equivalent data entry system. As an alternativeto the switch 236, the RFID tag 102 may be kept inactive by placing itin an RFID blocking sleeve. When the RFID tag 102 is inactive, it doesnot respond to reading by a reader. Thus, activation reduces theeffectiveness of a malicious reader, because the RFID tag 102 may beinactive when the malicious reader attempts to read it.

The display 238 displays information related to the operation of theRFID tag 102. (If such information display is undesired, the display 238may be omitted.) The display 238 may display status information, such aswhether the RFID tag 102 has successfully communicated with a reader ora server. The display 238 may display day, date or time information. Thedisplay 238 may also display authentication data such as a pseudorandomcomponent as described above (see step 126 of FIG. 2).

The power supply 240 may be used to power an active tag or to power theRFID tag 102 as required for synchronization with the server 106 (forexample, for synchronizing the generation of pseudorandom numbers asdescribed above with reference to FIG. 3). The power supply 240 may beomitted from the RFID tag 102 as desired, for example, in a passive tagor when synchronization with the server 106 is undesired.

The benefits realized by different embodiments or implementations of thepresent invention may include one or more of the following alone or incombination. First, the reader 104 need not decrypt the encrypted RFIDinformation. The reader 104 acts as a conduit for the encrypted RFIDinformation. Neither the server 106 nor the RFID tag 102 needs to“trust” the reader 104. Thus, even if an unauthorized reader reads theRFID tag 102, the unauthorized reader will have to expend significantprocessing resources in order to crack the encrypted RFID information.It therefore becomes unprofitable for a malicious entity to useunauthorized readers in an attempt to collect RFID information.

Second, the server 106 uses the authentication data to authenticate thereader 104. Even if an unauthorized reader reads the RFID tag 104 andsends a transmission to the server 106, the server 106 uses theauthentication data to reject the transmission. It therefore becomesunprofitable for a malicious entity to transmit unauthorizedtransactions to the server 106.

Third, the user may activate the RFID tag 102 prior to step 124. Priorto activation, the RFID tag 102 does not respond to being read. Suchactivation can take many forms, such as pushing a button, toggling aswitch, removing the tag from an RFID blocking sleeve, entering apassword, or providing biometric information (such as a fingerprint).Such activation prevents the RFID tag 102 from responding toindiscriminate reading, instead responding only after the user hasactivated the tag. It therefore becomes unprofitable for a maliciousentity to indiscriminately read RFID tags.

In this manner, the embodiments of the present invention address thesecurity concerns discussed above with reference to FIG. 1.

In one embodiment, the switch 236 may be used to activate the tag forfurther actions. However, in another embodiment, the tag may already beactive, and switch 236 may be used to verify information received from areader. For example, a tag may be in an active state for communicatingwith a reader. Before the tag sends information (e.g., an RFID) to thereader, it first may receive information from the reader, such as anumber, code, an image (e.g., a picture), or information about atransaction, which may be shown on a display 238, for example. A usermay be presented with information (e.g., on a display) received by thetag, and the user may verify the information by activating switch 236.In response to the user's activation of the switch, the tag may send thetag ID to the reader. Accordingly, a switch 236, which may be one switchor multiple switches, may be used to activate the tag or authorize thetag to send the tag identification, or both. Verification of informationreceived from a reader, and authorization using a data input system suchas a switch, allows the system to avoid access to a tag by maliciousreaders.

The above description illustrates various embodiments of the presentinvention along with examples of how aspects of the present inventionmay be implemented. The above examples and embodiments should not bedeemed to be the only embodiments, and are presented to illustrate theflexibility and advantages of the present invention as defined by thefollowing claims. Based on the above disclosure and the followingclaims, other arrangements, embodiments, implementations and equivalentswill be evident to those skilled in the art and may be employed withoutdeparting from the spirit and scope of the invention as defined by theclaims.

1. A method of transmitting information between a radio frequencyidentification (RFID) tag and a server, said method comprising the stepsof: encrypting, by said RFID tag according to a predetermined scheme,identification data identifying said RFID tag, to result in encryptedRFID information; reading, by a RFID reader, said encrypted RFIDinformation from said RFID tag; transmitting, from said RFID reader tosaid server, a transmission, wherein said transmission includes saidencrypted RFID information; and decrypting, by said server according tosaid predetermined scheme, said encrypted RFID information to producesaid identification data.
 2. The method of claim 1, further comprising:authorizing, by said server, said transmission using said identificationdata.
 3. The method of claim 1, further comprising: receiving, by saidRFID reader, authentication data, wherein said authentication dataauthenticates said RFID tag to said server, and wherein saidtransmission, from said RFID reader to said server, includes saidauthentication data; authenticating, by said server, said transmissionusing said authentication data and said identification data.
 4. Themethod of claim 3, wherein: said step of receiving comprises receiving,by said RFID reader, said authentication data and transactioninformation, wherein said authentication data authenticates said RFIDtag to said server, and wherein said transaction information relates toa transaction involving said RFID tag and said RFID reader; and saidstep of transmitting comprises transmitting, from said RFID reader tosaid server, said transmission, wherein said transmission includes saidencrypted RFID information, said transaction information, and saidauthentication data.
 5. The method of claim 4, further comprising:authenticating, by said server, said transaction using saidauthentication data and said identification data; and authorizing, bysaid server, said transaction using said identification data and saidtransaction information.
 6. The method of claim 3, wherein saidauthentication data comprises a password, biometric information, or apseudo-random number.
 7. The method of claim 3, wherein said RFID tagdisplays an authentication code that a user of said RFID tag provides tosaid reader as said authentication data.
 8. The method of claim 1,further comprising: activating said RFID tag, prior to said step ofreading.
 9. The method of claim 1, further comprising: activating saidRFID tag, prior to said step of reading, with one of a switch, biometricinformation, or a password.
 10. The method of claim 1, furthercomprising: generating, by said RFID tag prior to said step ofencrypting, a pseudorandom number, wherein said step of encrypting isperformed using said pseudorandom number.
 11. The method of claim 1,wherein said server generates an encryption key and transmits saidencryption key to said RFID tag, wherein said RFID tag uses saidencryption key when encrypting, and wherein said server uses saidencryption key when decrypting.
 12. The method of claim 1, wherein saidserver generates an encryption key and transmits said encryption key tosaid RFID tag, wherein said RFID tag updates said encryption keyaccording to a defined process to result in an updated encryption key,wherein said RFID tag uses said updated encryption key when encrypting,wherein said server updates said encryption key according to saiddefined process to result in said updated encryption key, and whereinsaid server uses said updated encryption key when decrypting.
 13. Themethod of claim 1, wherein said step of reading is performed bybackscattering.
 14. An apparatus including a radio frequencyidentification (RFID) system, said RFID system comprising: an RFID tag;an RFID reader that communicates with said RFID tag; and a server thatcommunicates with said RFID reader, wherein said RFID tag encrypts,according to a predetermined scheme, identification data identifyingsaid RFID tag, to result in encrypted RFID information, wherein saidRFID reader reads said encrypted RFID information from said RFID tag,wherein said RFID reader transmits a transmission to said server,wherein said transmission includes said encrypted RFID information, andwherein said server decrypts, according to said predetermined scheme,said encrypted RFID information to produce said identification data. 15.The apparatus of claim 14 wherein said server authorizes saidtransmission using said identification data.
 16. The apparatus of claim14 wherein said RFID reader receives authentication data, wherein saidtransmission, from said RFID reader to said server, includes saidauthentication data, and wherein said authentication data authenticatessaid RFID tag to said server.
 17. The apparatus of claim 16 wherein saidserver authenticates said transmission using said authentication dataand said identification data.
 18. The apparatus of claim 16, wherein:said RFID reader receives said authentication data and transactioninformation, wherein said transaction information relates to atransaction involving said RFID tag and said RFID reader; saidtransmission includes said encrypted RFID information, said transactioninformation, and said authentication data; said server authenticatessaid transaction using said authentication data and said identificationdata; and said server authorizes said transaction using saididentification data and said transaction information.
 19. The apparatusof claim 14, wherein said RFID tag comprises: a transceiver thatcommunicates with said RFID reader; and a processor, coupled to saidtransceiver, that encrypts, according to said predetermined scheme, saididentification data.
 20. The apparatus of claim 14, wherein said RFIDtag comprises: a transceiver that communicates with said RFID reader; amemory that stores a plurality of encryption keys; and a processor,coupled to said transceiver and to said memory, that encrypts, accordingto said predetermined scheme, said identification data using a selectedone of said plurality of encryption keys.
 21. The apparatus of claim 14,wherein said RFID tag comprises: a switch that activates said RFID tag;a transceiver that communicates with said RFID reader when said RFID tagis active; and a processor, coupled to said switch and to saidtransceiver, that encrypts, according to said predetermined scheme, saididentification data.
 22. The apparatus of claim 14, wherein said RFIDtag comprises: a switch that activates said RFID tag, wherein saidswitch includes one of a physical toggle, a biometric sensor, or apassword processing system; a transceiver that communicates with saidRFID reader when said RFID tag is active; and a processor, coupled tosaid switch and to said transceiver, that encrypts, according to saidpredetermined scheme, said identification data.
 23. The apparatus ofclaim 16, wherein said RFID tag comprises: a transceiver thatcommunicates with said RFID reader; a processor, coupled to saidtransceiver, that encrypts, according to said predetermined scheme, saididentification data; and a display, coupled to said processor, thatdisplays an authentication code that a user of said RFID tag provides tosaid RFID reader as said authentication data.
 24. A method oftransmitting information between a radio frequency identification (RFID)tag and a server, said method comprising the steps of: transmittingidentification data from said RFID tag to an RFID reader; receiving, bysaid RFID reader, authentication data, wherein said authentication dataauthenticates said RFID tag to said server; transmitting, from said RFIDreader to said server, a transmission, wherein said transmissionincludes said identification data and said authentication data; andauthenticating, by said server, said transmission using saidauthentication data and said identification data.
 25. The method ofclaim 24, wherein said authentication data comprises a password.
 26. Themethod of claim 24, wherein said authentication data comprises biometricinformation.
 27. The method of claim 24, wherein said authenticationdata comprises a pseudo-random number.
 28. The method of claim 27,wherein said pseudo-random number is generated by said RFID tag anddisplayed to a user, and wherein said server includes a synchronizedpseudo-random number.
 29. A method of transmitting information between aradio frequency identification (RFID) tag and a RFID reader, said methodcomprising the steps of: receiving, by said RFID tag from said RFIDreader, first information; displaying at least a portion of the firstinformation to a user; receiving a verification from the user to verifythe first information; and transmitting identification data from saidRFID tag to said RFID reader if the first information has been verified.30. The method of claim 29, wherein said step of receiving averification comprises activating a switch on said RFID tag to verifythe first information.
 31. The method of claim 29, wherein said firstinformation comprises information about a transaction.
 32. The method ofclaim 29, wherein said first information comprises a number or a code.33. The method of claim 29, wherein said first information comprises animage.
 34. An apparatus including a radio frequency identification(RFID) tag for use in an RFID system including an RFID reader and aserver, said RFID tag comprising: a transceiver that communicates withsaid RFID reader; and a processor, coupled to said transceiver, thatgenerates a pseudorandom number according to a predetermined scheme, andthat encrypts identification data identifying said RFID tag using saidpseudorandom number.
 35. The apparatus of claim 34, wherein said RFIDtag further comprises a switch for activating said RFID tag.
 36. Theapparatus of claim 34, wherein said RFID tag further comprises a switch,where said RFID tag receives information from a reader, and a userverifies the information from the reader and activates the tag using theswitch, and said RFID tag transmits information to the reader only ifsaid user verifies the information from the reader.
 37. The apparatus ofclaim 34, wherein said RFID tag further comprises a display, and whereinsaid RFID tag receives information from a reader and displays theinformation to a user.
 38. The apparatus of claim 34, wherein said RFIDtag further comprises a display, coupled to said processor, thatdisplays said pseudorandom number.
 39. An apparatus including a radiofrequency identification (RFID) tag for use in an RFID system includingan RFID reader and a server, said RFID tag comprising: a transceiverthat communicates with said RFID reader; a processor, coupled to saidtransceiver, that encrypts, according a predetermined scheme,identification data that identifies said RFID tag, and that generates anauthentication code; and a display, coupled to said processor, thatdisplays said authentication code.
 40. The apparatus of claim 39,wherein said RFID tag further comprises a switch for activating saidRFID tag.
 41. The apparatus of claim 39, wherein said RFID tag receivesinformation from a reader and displays the information to a user.
 42. Anapparatus including a radio frequency identification (RFID) tag for usein an RFID system including an RFID reader, said RFID tag comprising: aswitch for activating said RFID tag; a transceiver that communicateswith said RFID reader; and a processor, coupled to said transceiver,that processes information received from said RFID reader.
 43. Theapparatus of claim 42, further comprising a display, coupled to saidprocessor, that displays information received from said RFID reader. 44.The apparatus of claim 42, wherein said RFID tag receives firstinformation from said RFID reader if said switch is activated and saidtransceiver is disabled if said switch is deactivated.